SG Optimizer will go through all the code for your theme and plugins looking for things that won’t work with PHP 7.0. Once the plugin is done with its analysis, it gives you a list of any problems that it finds.
What do you do if your WordPress theme isn’t mobile friendly? My advice is to install the WPTouch plugin. It will make your site look good on mobile devices. It’s what I recommend to clients and it’s what I use on my own sites. Here are some things you should know